Method for preventing the loss of drilling fluid during the drilling of wells



J. F. LARKIN Feb. 22, 1944..`

METHOD FOR PREVENTING THE LOSS OF DRILLING FLUID DURING THE DRILLING OF WELLS Filed May 8, 1940 INVENTOR ATTORNEY METHOD FCR PREVENTING THE LOSS F DRILLING FLUD DURING THE OF WELLS Damme `iames F. Larkin, Oklahoma City, Okla.; Katharine Larkin Angus, administratrix of James Francis Larkin, deceased Application May d, i940, Serial No. 333,969

2 Claims. ("CL 16S-22) until a suiilcient amount of the fibrous material used lodges in the particular formation or formations into which` the fluid is escaping, and by its bulk completely fills up the crevices, fissures,A pores,

- etc., of the formation or formations. This method is costly, however,l because a continuous ow of liquid is necessary to carry the fibrous material into the cracks and ssures, and a continuous ow of liquid means the loss of an enormous quantity of drilling fluid before the fibrous material is deposited in suflicient quantity to completely fill the cracks and' crevices, This loss of the drilling uid, as stated, is very expensive, hundreds of tons sometimes being lost in a single well.

It is the chief object of the present invention to provide a method and meins for stopping up or plugging the cracks, crevices, fissures, etc., in

underground formations -at their mouths, eliminating the necessity of completely filling the remote recesses of those cracks, crevices, etc., with a consequent reduction in the amount of uid ordinarily lost during the stopping up or sealing 'of such cracks,`etc., and a similar reductionin the amount of sealing or plugging material required. Like characters of reference designate like parts in the gure. Qne embodiment is shown in the gure; the gure is a vertical sectional view I .through a portion of the earth depicting the mechanism for carrying out the method operatively installed therein.

The invention contemplates the use of small pieces of sponge rubber, in place of any of the brous materials above mentioned, to stop up the cracks, crevices, and fissures at or near their respective mouths. Sponge rubber, naturally, may rbe comparatively easily compressed to apprommately one-fourth of its normal volume Without in any way effecting its ability to reasume its normal size after the pressure is removed. It is an ideal material for this purpose because when itis compressed into the mouths of cracks and crevices, its inherent ability to expand holds it firmly in position even after the original compressing force is completely removed. According to the invention, when escape of the mud and consequent loss of circulation during drilling is noticed, the mud pump, which .is used to circulate the mud in the hole during the drilling operation, is shut olf. Naturally, the mud level lowers to a point adjacent the lowermost cracks and crevices into which the mud is eacaping. The drill stem may then be removed and a quantity of small pieces of sponge rubber may be introduced into the Well. e

By volume displacement, the sponge rubber causes the level of the drilling iiuid standing inl the hole to rise. Ordinarily this fluid level rise vwill be sufficient to start the fluid iioWing out through most all of the cracks .and crevices, and this outow carries the pieces of sponge rubber into the mouths of the cracks and crevices. In view ef the fact that there is' no forced circulation of fluid a-t this time, and hence no fluid pressure to rapidly force the fluid into the cracks 'and crevices, the fluid ow is slow, and the small a dam or log jamb across the mouths of the e cracks, much as a log jamb is formed in a flowing river. pieces continues until the entire mouth of each crack and crevice is plugged. As the mouth of each crack is plugged, the fluid rises above that point, and the head pressure created serves to compress and compact the various pieces of sponge rubber more tightly into the mouth of the submerged crack or opening. The drill stem may then be replaced, the mud pumps started, and the fluid level in the hole raised above the plugged cracks and ssures to test Whether or not the leaks in the formation have been sealed by the sponge rubber. If the leakage has been stopped, drilling fluid circulation and drilling may then be resumed and the head pressure of the column of iiuid in the hole further compresses the individual pieces of'sponge'rubber and forces each conglomerate plug more r'mly into its particular crack or crevice. Thus when the pressure is again removed from the drilling uid, th'.- expansion of the individual pieces attempting to resume their natural sizes and shapes holds tne'n nrmly witnin the mouths of the variouscreices. Such is This accumulation of sponge rubber into the wen through the drin stem, asiliustratea in the drawing, in a. manner similar to the mannerin which cotton seed hulls or any other fibrous material is now introduced into wells', as previously mentioned. The pumping of this sponge rubber impregnated drilling fluid into the well carries additional quantities of the spongy material to the mouths of the leaking cracks and crevices, but the actual loss ofv drilling fluid is small because the mouths of the cracks and crevices are already partially plugged.

When a sufficient quantity of the material has accumulated to completely plug the mouths of the lowermost cracks in the hole, the fluid level rises and carries additional sponge rubber pieces into the mouths of the cracks and crevices l- 'cated at a higher elevation. Also as the fluid rises above certain plugged cracks, the pressure on the elastic spongy -material plugging those cracks increases, thus compressing ythe material and making room for additional pieces of sponge rubber in the mouths of those particular cracks. The sponge rubber pieces are thus wedged tightly into the mouths of the cracks, much as a cork is used to plug the mouth of a bottle.

After sulcient time has elapsed, the formation is again tested for leakage, as previously described, and if it is found that mud still escapes, the pump is promptly shut oil to permit an additional quantity lof the sponge rubber pieces to be similarly introduced into the drilling fluid. When such a test shows that. the leakage has been stopped, drilling and the attendant circulation of plain drilling fluid is resumed, and the pres-y sure of the'v mud column outside the drill stem compresses and forces the various pieces of sponge rubber more tightly into the mouths of the plugged cracksand crevices of the porous forma,-

tion. Naturally when the pump pressure is removed, the various pieces 'of sponge rubber comtend to expand, which tendency causes a firm contact against the sides of the cracks, and holds i pressed into the mouths of the cracks and crevices Y.

the conglomerate plugs in their respective posiintroduced through the ,drill stem, as explained in the latter part of the above description.`

From the above description it-willbe seen that the use of my method produces three ve im-r portant results:

1. It generally reduces the amount of drillingfluid lost during the treatment of a well to seal or plug its cracks and crevices.

the welldrops to zero during hailing out of the drilling fluid.

In the drawing the numeral 6 designates a drill stem as a whole, numeral I designates a bit on the lower end of the stem; a circulation duct through the bit 'I is indicated by the dotted lines 8; the fluid level to which the mud settles in the well 9, after the pump pressure has been shut off, is indicated by the numeral I0, while the dotted line I I indicates the approximate height to which the mud level rises due to the expansion of the various small pieces I2 of sponge rubber. The v arious cracks and crevices of the porous formation 5 are designated by the numerals I3 and Il.

Having described the invention, what is claimed is:

-pieces of sponge rubber into the mud in the well;

raising the liquid level of the mud in the well by fluid pressure applied at the original point of introduction, to a point where escape of mud is noticeable; removing the fluid pressure'to allow the sponge rubber particlesv to expand, and to be carried by the consequent further rise of the fluid level of the -mud into the cracks and crevices;

and then flowing the mud underpressure upward through the well to force the sponge rubber pieces further into said cracks and crevices.

2. The method of plugging cracks and ssures in an underground formation penetrated by a well bore which comprises thesteps of illling the well bore with a liquid up to a point near the level of the lowermost cracks to be plugged, introducing a quantity of small pieces of sponge rubber into the .well bore, and applying fluid pressure to compress and force said sponge rubber pieces into the mouths of said cracks, where they are' lodged by their own expansion when the fluid pressure is removed. y

JAMES F. LARKIN. 

